1. Field of the Invention
The present invention relates to a heat exchanger with flat tubes, and more particularly, to a heat exchanger with flat tubes that can improve the heat exchange efficiency by making capacities of channels of each flat tube different from each other.
2. Description of the Related Art
Generally, an air conditioner for cooling interior air using a cooling cycle includes a compressor for compressing refrigerant to a high pressure, a condenser for exchanging heat of the compressed refrigerant with exterior air to liquefy refrigerant gas, and an evaporator for exchanging heat of the liquefied refrigerant with the interior air using an expansion valve or capillary tubes to evaporate the liquefied refrigerant. The air conditioner performs the cooling operation by using heat of gasification of refrigerant.
Thus, the air conditioner is configured to control the temperature of an enclosed space by inducing a phase transition of the refrigerant using a heat exchanger such as the condenser and the evaporator. Therefore, in order to improve the cooling efficiency, it is very important to improve the efficiency of the heat exchanger.
Due to the above reasons, in recent years, there appears a super compact condenser (SCC), which is designed to dramatically improve the heat-exchange efficiency by arranging a plurality of flat tubes in a zigzag-shape to allow the refrigerant to simultaneously flow. FIG. 1 shows a conventional heat exchanger with flat tubes used to perform heat exchange in an air conditioner using refrigerant.
Referring to FIG. 1, a heat exchanger with flat tubes includes first and second header tanks 10 and 20 disposed in parallel and spaced apart from each other at a predetermined distance, a plurality of refrigerant tubes 12 disposed in parallel and spaced apart from each other at a predetermined distance, opposite ends of each refrigerant tube 12 are configured to communicate with the first and second header tanks 10 and 20, respectively, and a plurality of cooling fins 14 formed on the refrigerant tubes 12 to discharge heat of the refrigerant flowing along the refrigerant tubes 12.
The first and second header tanks 10 and 20 are disposed facing each other, and refrigerant inlet and outlet tubes 16 and 18 are respectively connected to the first and second header tanks 10 and 20. In addition, at least one refrigerant separation membrane for directing refrigerant in a desired direction is disposed in the first and second header thanks 10 and 20.
In operation, the refrigerant introduced into the first header tank 10 through the refrigerant inlet tube 16 flow into the second header tank 20 along the refrigerant tubes 12 connecting the first header tank 10 to the second header tank
The refrigerant reciprocally flow between the first and second header tanks 10 and 20 by the separation membranes 22 disposed in the first and second header tanks 10 and 20, and are then discharged through the refrigerant outlet tube 18 of the second header tank 20 after repeatedly moved between the first and second header tanks 10 and 20. At this point, the refrigerant generate heat in the course of flowing along the refrigerant tubes 12, and the generated heat is radiated through the cooling fins 14 surface-contacting the refrigerant tubes 12. Since the heat exchanger is used as an evaporator or a condenser, it can function to increase or decrease the temperature of interior air.
FIG. 2 shows a sectional view taken along the line A–A′ of FIG. 1.
Referring to FIG. 2, the tube 12 is formed in a flat shape having a sectional structure in which refrigerant-flowing holes 12a of multi-channels Ch1–Chn are formed. Such a flat tube 12 is generally employed to a heat exchanger used as a high efficiency condenser.
The refrigerant is dispersed and flows along the refrigerant-flowing holes 12a configured in the multi-channels Ch1–Chn by a small amount. At this point, the dispersed refrigerant uniformly contacts an entire inner circumference of the respective refrigerant-flowing holes 12a by surface tension, so that an annular flow phenomenon is generated to increase the heat transfer efficiency. In addition, since an amount of the pressure drop is small, the flow of the refrigerant can be more stably realized.
Also, the refrigerant flowing along the header tanks 10 and 20 transfers heat through the cooling fins 14 surface-contacting an outer circumferences of the tubes 12 while passing through the multi-channels Ch1–Chn, i.e., the refrigerant flow holes 12a, thereby increasing or decreasing the air temperature.
Meanwhile, as described above, the refrigerant flow holes 12a of the flat tube are formed in a kind of the micro multi-channels Ch1, Ch2, . . . , Chn. Each of the channels has a rectangular section with an identical width. In addition, each of the foremost and rearmost channels Ch1 and Chn has a hemispherical outer end section to reduce the contact resistance with the air.
However, since the widths of channels are identical to each other and the intervals between the channels are also identical, it is difficult to maximize the heat transfer efficiency at a front end portion of the tube, thereby deteriorating the heat transfer efficiency of the heat exchanger.